Sagehen Creek Field Station

31 Jul, 05 AM - 31 Jul, 06 AM

Rapid climate change is altering species range boundaries, phenology, and genetics (Parmesan and Yohe 2003). As the climate continues to warm, modeling studies project that climate change will emerge as a leading cause of global biodiversity loss (Thomas et al. 2004, Loarie et al. 2008). However, predicting the fate of individual species in the face of climate change is complex because it requires identifying the precise mechanism that control distribution and abundance for each species (Hijmans and Graham 2006). The American pika (Ochotona princeps, henceforth simply pika), a small mammal (order Lagomorpha) that resides in high elevation talus habitat in California, has emerged as a model organism for studying the effects of climate change on montane small mammals (Beever et al. 2011, Erb et al. 2011, Stewart and Wright 2012, Jeffress et al. 2013). Pikas are well adapted to surviving cold winters under the snow, but evidence suggests they may be highly vulnerable to increases in summer temperature. Historical revisit studies in the Great Basin (Beever et al. 2011) and California (Stewart et al. in review) both indicate that summer temperature is the best climate predictor of extirpation. Models that predict pika occupancy as a function of summer temperature project that pikas could become extirpated from > 90% of their current habitat in California by the end of the 21st century (Calkins et al. 2012, Stewart et al. in review). The Pikas poor capacity to dissipate heat physiologically (MacArthur and Wang 1973) appears to force them to thermoregulate behaviorally, spending more time in underground and less time active above ground (Smith 1974) when high diurnal temperatures occur. The central hypotheses of this study are that heat stress results in (H1) reduced above ground activity, (H2) reduced ability to forage (e.g. energy budgets), and (H3) reduced fitness. While inductive reasoning supports these hypotheses, they have not yet been tested empirically. In addition to testing mechanisms of climate-mediated decline, a key goal of this proposal is to parameterize a behavioral and physiological model of pika demography and distribution that will give insight into the thresholds that lead to population collapse. I will use camera traps and audio recorders to observe pika behavior. Pikas are central place foragers and each camera will be aimed to capture activity at the center of the pikas territory. Camera traps and audio recorders are ideal for this application because they have minimal impact on animal behavior in contrast to observations from nearby humans. Because camera traps use IR-imaging to record behavior after dark they can be used to assess whether pikas are able to escape the constraints of daytime thermoregulation by foraging at night. During a period of human observations, the mass of plant matter collected orconsumed will be estimated in-situ, and samples will be collected forlaboratory measurement of energetic and water content. I will measure e by deploying fur-covered, copper-framed operative temperature models, designed to mimic the size, shape, and thermal properties of a pika. Operative temperature models, have been used for over 30-years (Dzialowski 2005) and have been shown to accurately predict body temperature in ectotherms and environmental heat flux in endotherms (Dzialowski 2005, Sinervo et al. 2010). Because operative temperature models mimic the physical properties of an animal and are deployed directly to the animals environment, they effectively distil multiple environmental measurements (e.g. ambient temperature, direct solar insolation, wind speed, and relative humidity) into a single measure of the effect they have on thermoregulation. e will be analyzed against weather data from Carpenter Ridge in order to model the pikas thermal environment as a function of commonly available weather variables. Because hundreds of other burrowing or saxicolous species employ similar behavioral thermoregulation to avoid acute heat stress, the methods I developed will be broadly applicable. In the course of my Masters research, I mentored 12 undergraduate volunteers, of which 92% have been from minority backgrounds underrepresented in science. I will seek funding to support additional assistants. After publication of relevant manuscripts, modeling code and data will be made publicly available. Further, my findings will inform managers of the risks posed by climate change to a litigated species.

Visit #36820 @Sagehen Creek Field Station

Approved

Under Project # 29518 | Research

Hours of activity and energy budgets for the American pika.

graduate_student - University of California, Santa Cruz

Reservation Members(s)

April Fong Jul 31, 2014 (1 days)
Joseph Stewart Jul 31, 2014 (1 days)

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Day Use (suggested) 2 Jul 31 (1 hours)